确定管道的大小，而不调用阅读（） [英] Determine the size of a pipe without calling read()

问题描述

我需要一个叫做SizeOfPipe（）函数应返回一个用户喉─我只想知道多少数据是在管道和实际上不脱管本身读数据的大小。

I need a function called SizeOfPipe() which should return the size of a pipe- I only want to know how much data is in the pipe and not actually read data off the pipe itself.

我觉得以下code将工作

I thought the following code would work

fseek (pPipe, 0 , SEEK_END);
*pBytes = ftell (pPipe);
rewind (pPipe);

但文件描述符fseek的dosent工作。另一种办法是阅读管道，然后将数据写回，但想如果possibe，有什么建​​议？

but fseek dosent work on file descriptors. Another option would be to read the pipe then write the data back but would like to avoid this if possibe, any suggestions ?

推荐答案

根据您的UNIX实现的ioctl / FIONREAD可能做的伎俩

Depending on your unix implementation ioctl/FIONREAD might do the trick

err = ioctl(pipedesc, FIONREAD, &bytesAvailable);

除非本返回错误code为无效的参数（或任何其他错误）信息bytesAvailable包含的数据可当时疏通读操作的数量。

Unless this returns the error code for "invalid argument" (or any other error) bytesAvailable contains the amount of data available for unblocking read operations at that time.

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